Birth control pills are a pill you take everyday to prevent pregnancy. The most effective way to take pills is if you take them at the same time every day and if you do so they are 98-99% effective. The pills work by releasing hormones that keep your ovaries from releasing eggs. The hormones also thicken your cervical mucus, which helps to block sperm from getting to the egg in the first place.
They do not prevent STD's. Side effects are...sore breasts, nausea, spotting, and decreased sex drive. The pill has to be prescribed to you by a doctor and could range in price from $0 to & $90